Drerok,
I'm gonna have to agree, I don't think the issue is water. Burning oil when coming off the highway I again agree it is more than likely turbo seals not maintaining pressure. As far as the back-firing, does the car hesitate when you're driving through town? You may be looking at plugs that are not burning the fuel in the chamber, moving past the turbo at +/- 2500 degree's may be causing the back-fire. May also concider why there is fuel loading up. I'd start with the plugs, wires, easy fix (also routine maintanence) then I would look at the pressure regulater. If it's loading up and back-firing it's gonna be fuel that isn't burning you just have to find out where and why. Good luck, Antz